Agricultural harvesting machines, such as draper platforms, include a reciprocating knife disposed at the leading edge of the harvesting machine. These reciprocating knives are formed of an elongate bar to which many small knife blades are attached. The elongate bar is driven back and forth, in a direction parallel to the longitudinal extent of the reciprocating knife. The reciprocating knife also includes knife guards that extend generally fore and aft (i.e. a direction perpendicular to the longitudinal extent of the elongate bar). The knife guards serve as stationary guides that divide the crop every few inches. The knife guards also have fore and aft extending knife edges against which the edges of the small knife blades.
Drive mechanisms of a variety of constructions are coupled to the elongate bar and drive the elongate bar back and forth. This causes the small knife blades to slide back and forth with respect to the knife guards and to sever crop plants that are caught between the small knife blades and the knife guards.
At the same time that the reciprocating knives have been increasing in length, the reciprocating knives have been designed to flex up and down following the contours of the land over which they travel. This permits the reciprocating knives to more closely follow the contours of the land over which they travel. In order to have a flexible reciprocating knife, the elongate bar cannot be increased in its cross-sectional dimensions, since any increase in cross-sectional dimensions would make the elongate bar more rigid and less able to flex. In order to the now-heavier reciprocating knives of modern designs, the couplers that attach to the elongate bar to and drive it are made longer and longer.
One problem with this arrangement is that the couplers are made longer, and are attached over greater length to a relatively flexible elongate bar. This causes stresses in the elongate bar that cause the elongate bar to break.
It is an object of this invention to provide a drive coupler for a reciprocating knife of an agricultural harvesting machine that reduces the stresses in the elongate bar of the reciprocating knife and reduces the probability that it will fatigue under the reciprocating loads and break.